Accuracies of conventional low frequency clock signals are commonly determined by a resolution of a controllable oscillator. Since a resolution of a control signal used by the oscillator is often fixed, the accuracy of the low frequency clock signal is also fixed. Drift and cycle-to-cycle jitter can be less than a least significant bit of the control signal and so cannot be corrected by adjusting the control signal.
It would be desirable to implement a frequency synthesizer with tunable accuracy.